In file included from main.cpp:8:0:
num.cpp:14:5: error: prototype for 'Num Num::operator=(const Num&)' does not match any in class 'Num'
 Num Num::operator=(const Num &other) {
     ^~~
In file included from main.cpp:7:0:
num.h:7:10: error: candidate is: Num& Num::operator=(const Num&)
     Num& operator=(const Num& other);
          ^~~~~~~~